Method and device for filling seal caps

ABSTRACT

Described herein is a method for filling seal caps and also to a corresponding automated device for filling seal caps. The method for filling seal caps includes carrying out the filling of the seal caps using an automated process, where positioning a filling unit and/or positioning the seal caps by means of movement in an XYZ coordinate system as well as filling the seal caps is automated, and where the seal caps are positioned on a support plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/320,705, filed Jan. 25, 2019, which is a U.S. National PhaseApplication of PCT/EP2017/068793, filed on Jul. 25, 2017, which claimsthe benefit of priority to German Patent Application No. 10 2016 213669.0, filed Jul. 26, 2016 and to German Patent Application No. 10 2016214 201.1, filed Aug. 2, 2016, each of which is incorporated byreference in its entirety herein.

BACKGROUND

Within the aircraft industry, rivets or rivet heads are typically coatedwith a sealing agent (sealant) or, in the cured state, with a seal cap,in order to seal them off or to provide protection from corrosion. Thesealing agent is generally applied manually, carried out for examplewith cartridge guns that are guided by hand.

As an alternative to this, it is also possible to use seal caps, whichare produced from sealing agent but have already undergone curing, thesecaps being supplied in a corresponding contour to the rivet or the rivethead. These cured seal caps may then be used further in a variety ofways:

In one instance, the cured seal caps may be filled with fresh sealantand deep-frozen in order to prevent the sealant reacting. Shortly beforeuse, the caps are thawed and are then ready for service. This method,however, has the disadvantage that the seal caps filled with frozensealant have only a limited storage life, must first be conditionedprior to service, and, moreover, carry a risk of forming condensation.Another disadvantage lies in the logistical chain, which requires rapidtransport and also the provision of deep freezers.

Alternatively, the seal caps may also be filled with sealant manually,using a cartridge gun, directly before their application, after whichthey are processed. This method, however, is unable to ensure uniformfilling of the seal caps, since in this operational step they cannot beweighed. The amount injected may therefore also be over or underdosed.This procedure, moreover, is very time-consuming and inconvenient,requiring the handling simultaneously of cartridge gun and sealant cap,and requiring the cap to be mounted promptly.

BRIEF SUMMARY OF THE INVENTION

It was an object of the present invention, therefore, to provide amethod for filling seal caps that does not have the disadvantagesidentified above. The filling of the seal caps with sealant is to takeplace in particular in a time-saving manner but with high quality, andat the same time is to result in a reduction in cost.

The underlying object of the present invention is achieved by means ofthe method according to claim 1. Preferred embodiments are specified inthe dependent claims.

The method of the invention can be used for filling seal caps which havealready undergone curing. In that case the filled sealant may be frozen,as described above, to be used after a certain storage time, or else, aslikewise already set out above, can be filled shortly before the sealcap is mounted. With preference the seal caps are not frozen, but areinstead filled shortly before being mounted, thereby allowing the coststo be reduced, since there is no need for deep freezers to be providedand also no need to maintain a cooling chain.

In the method of the invention for filling seal caps, the filling of theseal caps is carried out automatedly, wherein the positioning of thefilling unit and/or the positioning of the cured seal caps by means ofmovement in XYZ direction as well as the filling of the seal caps takeplace automatedly and wherein the cured seal caps are positioned on asupport plate. Relative to the known, manual filling of the seal caps,this results in a time saving of up to 100%.

The automation of the filling procedure is for example under softwarecontrol, with either the seal caps located on the support plate and/orthe filling unit of the device, from which the sealant is filled intothe seal cap, being moved in X, Y or Z direction. Preferably this isdone using a robot or a similar device with XYZ travel, allowing eitherthe support plate together with the seal caps, and/or the filling unit,to be moved automatedly in order for the sealant to be filled in oncorrect positioning.

In a further-preferred embodiment, the method of the invention may alsocomprise the automated mounting of the seal cap after it has beenfilled.

The object on which the present invention is based is further achievedby the device according to claim 10.

In accordance with the invention, a device or robot of this kindcomprises

-   -   a filling unit with which the sealant is filled into the seal        cap;    -   a support plate on which the cured seal caps are located;    -   a displacement travel unit with which either the filling unit        and/or the support plate can be moved, preferably by means of        corresponding motorization; and    -   a control unit with which the movement of the filling unit        and/or the support plate and the filling are regulated, with        each of the displacement travel unit and the filling unit being        controlled by the control unit.

BRIEF DESCRIPTION OF DRAWINGS

An example of a corresponding robot is illustrated in FIGS. 1 to 6.

FIG. 1: View of the robot from diagonally above. Visible here is thebase of the robot, which serves for the fastening of the support plate.

FIG. 2: Front view of the robot.

FIG. 3: Side view of the robot. The filling unit here comprises acartridge with mixed sealant, which is fastened on a metering head.

FIG. 4: Schematic diagram of the top section view of a filled seal capin accordance with an exemplary embodiment.

FIG. 5 is an illustration of a method for filling seal caps inaccordance with an exemplary embodiment.

FIG. 6 is a block diagram of the control unit in accordance with anexemplary embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, in one aspect of the invention, a device orrobot 10 has a base 11, a support plate 12, a filling unit 13, adisplacement travel unit 14 and a control unit 15. The filling unit 13fills sealant 16 into a seal cap 17. The support plate 12 is fastened tobase 11 and a seal cap 17 is positioned on the support plate 12. Thefilling unit 13 includes an extrusion unit 18, which has a metering head19, such as a compressed-air drive or servo drive. The extrusion unit 18may be a cartridge extrusion unit as shown in FIGS. 1-3. A cartridge 20with mixed sealant 16 may be inserted into the extrusion unit 18 andfastened to the metering head 19. In one aspect, the cartridge extrusionunit 18 includes a piston 21.

A filled seal cap 17 is shown in FIG. 4. The sealant 16 may include afiller, such as hollow filling bodies filled with gas and/or air. In oneaspect, the hollow filling bodies filled with gas and/or air aremicroballoons 22.

The filling unit preferably comprises an extrusion unit with which thesealant is pressed from a corresponding container into the seal cap. Thedevice of the invention to be used comprises more particularly acartridge extrusion unit with compressed-air drive or servo drive asfilling unit, and cartridges filled with ready-made sealant are insertedinto the extrusion unit, from which cartridges the sealant is thenextruded on filling. It is, however, also possible for the extrusionunit to comprise a mixing vessel in which, from two different lines, thetwo components are filled in and subsequently mixed, so that the sealantis produced directly prior to filling.

The cartridge extrusion unit preferably has a servo drive. In this casethe cartridge is filled with the sealant and is pressed out by means ofa piston which is controlled via the servo drive. With particularpreference the servo drive is suitable for two different cartridge sizeswhich are commonplace within the aircraft industry. As a result, thereis no need for an air-assisted pressing unit, and so compressiblesealants (sealants which are not newtonian fluids and which arecompressed during extrusion) can be used.

In one preferred embodiment of the present invention, the automateddevice is portable. In this case, then, the device has dimensions and aconfiguration such as to allow a rapid set-up and take-down of thedevice. A portable device allows set-up directly at the premises of theuser, who is able consequently to mount the seal caps on the respectiverivet or rivet head without a time delay.

The significant increase in operating speed as a result of filling bymeans of an automated device, such as a suitable robot system, forexample, also allows an increase in the cycle rate in aircraftconstruction if the activities performed manually during the filling andmounting of the seal caps are reduced.

Where a suitable robot system is used, the average time for the fillingof a seal cap with sealant is, for example, only 2.5 seconds. Incomparison to this, in the case of manual filling, the procedure istime-consuming.

The automated device, preferably the robot, is able to inject thesealant, in one preferred embodiment, into the seal caps in thearrangement dictated by the support plate. The seal caps in this caseare fastened in a freely selectable arrangement on the support plate,this arrangement of the seal caps on the support plate either havingbeen programmed into the software of the control unit beforehand, or thecontrol unit comprising a—for example—optical recognition unit which iscapable, during or before the filling of the seal caps, of determiningthe position of the other seal caps and directing them correspondinglywith the filling unit. FIG. 6 provides a block diagram of the controlunit in accordance with an exemplary embodiment. With reference to FIG.6, the control unit 15 includes an optical recognition unit 150.

The number of seal caps on the support plate can be varied within a widerange and is dependent only on the size of the seal cap in relation tothe size of the support plate. The seal caps can also be positioned onthe support plate in such a way that the positioning pattern on thesupport plate is similar to or indeed corresponds to the positioningpattern of the rivets or rivet heads on the actual component. This makesit easier to recognize the correct position for the seal cap to beapplied. FIG. 5 provides an illustration of a method for filling sealcaps in accordance with an exemplary embodiment. With reference to FIG.5, seal caps are filled with sealant using an automated process 100, afilling unit and/or seal caps are positioned by means of automatedmovement in an XYZ coordinate system 200 and the seal caps arepositioned on a support plate in a positioning pattern corresponding toa positioning pattern of connecting elements to be sealed 300.

The robot is able to inject the sealant, in one preferred embodiment,into the seal caps in the contour dictated by the support plate.

The amount of sealant to be injected is dependent on user requirementsand may be specified for each seal cap in accordance with its geometryand with the geometry of the rivet or rivet head. In one preferredembodiment, prior to the filling, the standardized amount for theparticular size of seal cap is stored in a suitable program of thecontrol unit. On the basis of these stored data, the automated device,preferably the robot, is then able to fill the respectively correctamount into the seal cap.

As a result, over and/or underdosing of the seal cap with too little ortoo much sealant is avoided. At the same time, the formation ofcondensation by the thawing seal caps with sealant prepared by mixing isprevented as well.

The extrusion rate or filling rate of the sealant, or the filling time,can be adjusted preferably via corresponding adjustments on the device,preferably the robot. The filling rate is preferably adapted to theproperties of the sealant, particularly the viscosity, the rheologyand/or the stringing. Through such adjustments, the aim is to achieve anoptimized filling pattern (height and silhouette of the filling in theseal cap) that meets the requirements of the user, particularly thesurface requirements imposed on the filling. In one preferredembodiment, the surface of the sealant filling has a planar or levelcross section and does not have an elevation which ends in a point andwhich is formed, for example, when the speed at which the filling unitlifts from the filling is not matched to the stringing properties of thesealant.

The cure rate of the sealant in the seal cap may also be adapted byselecting a faster sealant, something which is not possible, incontrast, when using deep-frozen seal caps.

According to a first, especially preferred embodiment, the seal caps areplastic caps for the sealing of joining elements in aircraftconstruction, said caps consisting predominantly of at least onehigh-performance polymer and having a DIN IEC 60243 breakdown strengthof at least 10 kV/mm.

These plastic caps are filled with a sealant which has a high energyabsorbency and also with at least one filler selected from the groupconsisting of hollow filling bodies filled with gas and/or air. Theplastic caps and the sealant here are joined cohesively to one another.

Seal caps of this kind function as combined protection against fuel andhydraulic oil, especially that based on tributyl phosphate, and alsoagainst lightning strike, and can be produced and applied economically.

The following definitions are to apply here:

Reference presently to “high-performance polymer” is to homopolymers andcopolymers which are distinguished by high chemical stability andthermal stability.

The concept of the “plastic caps [ . . . ] consisting predominantly ofat least one high-performance polymer” means that they may also includean amount of less than 50 wt % of other constituents which are nothigh-performance polymers.

The phrase “the plastic caps and the sealant are joined cohesively toone another” should be understood to mean that the filled-in sealant andthe at least one high-performance polymer cannot be parted from oneanother without destruction or do not part under the conditions whichare usual in the operation of an aircraft.

The at least one high-performance polymer of the plastic caps isselected more particularly from the group consisting of polyvinylidenefluoride (PVDF), polysulfone (PSU), polyphenylene sulfone (PPSU),polyetheretherketone (PEEK), polyimide (PI), polyamideimide (PAI),polybenzimidazole (PBI), polyetherimide (PEI), and polyphenylene sulfide(PPS).

The sealant filled into the plastic caps is preferably a sealant basedon polysulfide and/or polythioether. With particular preference it is apolysulfide and/or a polythioether in combination with manganesedioxide, an isocyanate compound, an isocyanate prepolymer and/or anepoxide compound as hardener.

The use as fillers of hollow filling bodies filled with gas and/or airhas the advantage that the microcellular character of such bodies endowsthem with an energy-absorbing activity. The hollow filling bodies filledwith gas and/or air are preferably microballoons.

With seal caps of this kind, precise filling—of the kind enabled by thepresent invention—is particularly important, since expelled sealant isnot resistant to hydraulic oil.

According to a second especially preferred embodiment, the seal caps arecaps produced using nozzles described in EP 2 586 537 A1. These nozzlesfor the application of sealants have a nozzle tip in bell or cowl form,and a clamping ring on the injection side of an elongated nozzleelement. Injection may take place manually or with automated sealantinjection machines.

With seal caps of this kind, precise filling—as enabled by the presentinvention—is likewise particularly important.

1-9. (canceled)
 10. A device for filling seal caps, said devicecomprising: a filling unit with which sealant is filled into seal caps;a support plate on which the seal caps are located; a displacementtravel unit with which the filling unit and the support plate can bemoved in an XYZ coordinate system; and a control unit with which themovement of the filling unit and/or the support plate and the fillingare regulated, wherein the control unit comprises an optical recognitionunit for determining positioning of the seal caps on the support plate;and wherein the filling unit comprises an extrusion unit comprising aservo drive and a cartridge with sealant.
 11. The device according toclaim 10, wherein the device further comprises a base for attaching thesupport plate.
 12. The device according to claim 10, wherein the fillingunit further comprises a nozzle comprising a tip in cowl form or bellform.